The aim of this project is to investigate the chemical composition, antigenic structure and biological significance of the various substances at or near the surface of the streptococcal cell. The surface components concerned include the capsule, cell wall, the cell membrane and the teichoic acids. Individual protein and carbohydrate components of the cell wall are being studied in purified form and attempts are being made to determine the nature of their chemical combination at the cell surface. In addition to direct chemical and immuno-chemical analysis, biological approaches to an understanding of the cell surface include investigations of the interaction of the cell with bacteriophage and of the action of muralytic enzymes. The cellular immune response to the various components of the streptococcus in acute rheumatic fever and acute glomerulonephritis is being studied to evaluate their significance in the pathogenesis of disease.